Owners of digital content such as movies, television programs, advertisements, newscasts, sport telecasts, e-books, software, and video games naturally must distribute their digital content in order to profit. However, distribution of their digital content makes the content vulnerable to improper uses, such as illegal copying and re-distribution.
Digital rights management (DRM) are technologies used by content owners to control access to digital content. Using DRM, the content owner can achieve a variety of access controls such as requiring a license to play the digital content at all, preventing the digital content from being copied, limiting which device can play the digital content, placing an expiration date on playing the digital content, allowing the digital content to be played a certain number of times, etc.
A DRM process typically has an enforcement mechanism at the client device that plays the digital content in order to enforce a set of rules devised by the content owner. As an example, the owner might encrypt the digital content and provide a means to obtain cryptographic keys to unlock the digital content. The enforcement mechanism obtains the cryptographic keys and uses them to unlock the encrypted digital content. Moreover, the enforcement mechanism only allows certain actions to be performed, such as viewing the digital content once on a particular client. Thus, the digital content owner is able to control access to content by enforcing a set of access control rules.
However, in some cases an entity other than the digital content owner distributes the content, and thus may wish to enforce its own access restrictions. For example, a cable broadcaster might apply a set of access control rules to digital content such as television programs and advertisements that are not owned by the cable broadcaster. In such cases, the access control rules of the content distributor may be inconsistent with the desires of the content owners.
In many cases, the content distributor will be distributing digital content from many different content owners, and thus it can be very difficult to apply content restrictions that are appropriate for all entities. For example, if the most restrictive access control rules are applied when the access control rules are inconsistent, then an entity that desires less restrictive access control will not be satisfied.